tune up

can't carry a tune in a bucket

Sings very badly.

change one's tune

To reconsider; rethink; to reach a different conclusion.

sing a different tune

To hold a different opinion or appreciation (about something); to possess a new, changed, or regenerated mindset, usually for the better.

sing the same tune

To hold the same opinion or understanding as another; to be in agreement on a matter.

tune in

To pay attention.

tune out

To stop paying attention to; to ignore; to zone out.